1. Field of the Invention
The invention relates generally to methods and compositions for reducing the detrimental effects of plasma on metal oxide dielectric layers during plasma-enhanced atomic layer deposition (PEALD) of overlying conductive materials.
2. Description of the Related Art
Plasma-enhanced atomic layer deposition (PEALD) is a gas phase chemical process typically used to create extremely thin coatings. As in traditional atomic layer deposition (ALD) methods, in PEALD a reaction surface is alternately and sequentially contacted with reactants such that a thin film is deposited. In PEALD, one reactant is a plasma reactant, such as hydrogen (H*) plasma or hydrogen-nitrogen plasma (for example, NH*, NH2*, NH3*, or N*+H*). Frequently, a second reactant is an organometallic or inorganic metal source chemical.
PEALD can be used to deposit a number of refractory metals and conductive metal alloys. These materials can be used, for example, as gate electrodes or capacitor electrodes in integrated circuits devices. Frequently, a conductive layer is deposited on a metal oxide dielectric. Problems can arise when the plasma used in the deposition process reacts with the metal-oxide dielectric in the first few deposition cycles and at least partially reduces the metal-oxide dielectric back to unoxidized metal or to a substoichiometric metal oxide state. This can result in poor adhesion between the metal oxide dielectric and the overlying conductive material. While this affects the common metal oxides used in integrated circuit manufacturing, such as Ta2O5, TiO2, HfO2, ZrO2, Al2O3, La2O3, this effect is particularly pronounced with Al2O3 and increases as the plasma intensity (e.g., power, reaction time) increases.